VertebratesA Summary

Chapter 26

AP Biology Spring 2011

ChordatesVertebrates include:

FishAmphibiansReptilesBirdsMammals

Are coelomate, bilateral animals

Chordates Many of 4 anatomical features that

characterize chordates appear only during embryonic developmentNotochord: long, flexible rod that appears during

embryonic development between the digestive tube and the dorsal nerve cord

Dorsal, hollow nerve cord: formed from a plate of ectoderm that rolls into a hollow tube

Pharyngeal clefts: grooves that separate a series of pouches along the sides of the pharynx; in most chordates the clefts develop into slits that allow water to enter and exit he mouth without going through the digestive tract

A muscular tail posterior to the anus

VertebratesHave an internal skeleton and big brainInternal skeleton: enlcoses and protects

internal organs and works with muscles to produce movementHave several advantages of external

skeletons:Cells are living so skeleton foes not have to be

molted Allows for greater flexibility Is lightweight

VertebratesNotochord develops into

vertebral column which encloses and protects spinal cord

Have large brains with paired eyes and ears

With the exception of lampreys, have jaws

VertebratesCirculatory and respiratory system

Paired gills evolved in early vertebrates and allowed for faster, more efficient gas exchange

Before transition to land, several species of fish developed small outpouchings in the side of the gut that evolved into lungs

Have a closed circulatory system which makes circulation faster

Gradually, there was less reliance on gills and more on lungs and circulatory system (heart, blood vessels), which work in connection

VertebratesOther organ systems

Have paired kidneys to deal with internal fluid composition

Reproduce sexually Have well developed immune system

GnathostomesVertebrates that have jaws Jaws of vertebrates evolved from

modification of skeletal parts that had once supported the pharyngeal (gill) slits

GnathostomesClass Chondrichthyes: sharks and rays

Have flexible endoskeletons composed of cartilage, possess streamlined bodies, are denser than water, will sink if stop swimming

GnathostomesClass Osteichthyes: bony fish

Most numerous of vertebrate groupsTwo main classes of bony fish are ray finned

and lobed finsHave an ossified endoskeleton, covered in

scales, posses a swim bladder

PiscesFishAre cold blooded vertebrates that have:

GillsScalesTwo chambered heart

GnathostomesTetrapods that have four limbs and feetClass amphibia

Not all have legs Frogs

AmphibiaCold-bloodedInitially breath through gillsThen develop lungsCan also exchange gas through their moist

skin Have a three chambered heart Close ties with waterTheir eggs lack a shellFertilization is externalCan exhibit complex social behaviour

Amniotes Tetrapods that have a terrestrially adapted

eggConsist of mammals and reptiles and birds Amniotic egg

Important evolutionary development for life on land

Have shell that retains water and can be laid in a dry environment

Have extraembryonic membranes that function in gas exchange, waste storage and transport of nutrients to embryo

ReptiliaCold-bloodedHave eggs with a chitinous covering

Lay eggs on landUndergo internal fertilization

Have a four chambered heartFirst vertebrates to have internal fertilizationHave scales containing keratin

Adaptation for terrestrial living Obtain oxygen through their lungs, not skin

ReptiliaExtinct reptiles:

Dinosaurs (lived on land)Pterosaurs (flying reptiles)Plesiosaurs (marine reptiles)

Modern reptiles:Turtles, tuataras, lizards, snakes, alligators,

crocodilesMost are ectothermic

Regulate body temperature through behavioral adaptations rather than by metabolism

AvesBirdsWarm-bloodedHave eggs with shells

Lay amniotic eggsWings, feathers, hollow bonesFour-chambered heart

High rate of metabolism Have keratin containing scales on their legsScales and eggs are reptilian

characteristics

AvesMost birds bodies are constructed for flight:

Light, hollow bonesRelatively few organsWingsFeathers

Endotherms: maintain warm, consistent body temperature

Feathers and in some cases a layer of fat insulate birds and help maintain internal temperature

Have larger brains than amphibians and nonbird reptiles do

MammaliaWarm-blooded (endotherms)Active metabolism Most are born rather than hatched Use internal fertilization Large brainsFour-chambered heart Have hair and produce milk to feed their

young All have teeth of differing size and shape

MammaliaSome have a placenta (eutherians)

Structure that nourishes fetus Embryo develops internally in a uterus

connected to mother by placenta, where nutrients diffuse from mother to embryo

MammaliaMarsupials do not have a placenta

Developing embryo receives little nourishment from mother in the uterus

About eight days after fertilization, fetus must continue its maturation in mother’s pouch (nurses)

MammaliaMonotremes: egg laying mammals

Duck billed platypus and spiny anteater Derive nutrients from shelled egg

Mammalia: PrimatesHumans are primatesPrimates descended from insectivores,

probably from small, tree dwelling mammals

Have dexterous hands and opposable thumbs Make it possible to do fine motor tasks

Nails have replaced claws Hands and fingers contain many nerve

endings and are sensitive

Mammalia: PrimatesEyes are front facing and set close together

Front facing eyes fosters face-to-face communication

Close set eyes are responsible for overlapping fields of vision, which enhances depth perception and hand-eye cordination

Mammalia: PrimatesDevote much energy to parenting of young

Engage in most intense parenting of any mammal

Usually have single births and nurture young for long time period

Mammalia: PrimatesInclude:

HumansGorillasChimpanzeesOrangutansGibbons Old world and new world monkeys